A report declassified by the United Nations yesterday contained a hidden bombshell with the revelation that inspectors have recently discovered an undeclared Iraqi drone with a wingspan of 7.45 meters, suggesting an illegal range that could threaten Iraq's neighbors with chemical and biological weapons.

U.S. officials were outraged that Hans Blix, the chief U.N. weapons inspector, did not inform the Security Council about the drone, or remotely piloted vehicle, in his oral presentation to Foreign Ministers and tried to bury it in a 173-page single-spaced report distributed later in the day. The omission raised serious questions about Dr Blix's objectivity.

"Recent inspections have also revealed the existence of a drone with a wingspan of 7.45m that has not been declared by Iraq," the report said. "Officials at the inspection site stated that the drone had been test-flown. Further investigation is required to establish the actual specifications and capabilities of these RPV drones . . . (they) are restricted by the same UN rules as missiles, which limit their range to 150km (92.6 miles)."

Colin Powell, the U.S. Secretary of State, told the Security Council in February that Washington had evidence that Iraq had test-flown a drone in a race-track pattern for 500km non-stop.

In another section of the declassified report, the inspectors give warning that Iraq still has spraying devices and drop tanks that could be used in dispersing chemical and biological agents from aircraft. "A large number of drop tanks of various types, both imported and locally manufactured, are available and could be modified," it says.

The paper, obtained by The Times, details the possible chemical and biological arsenal that British and U.S. Forces could face in an invasion of Iraq. The paper suggests that Iraq has huge stockpiles of anthrax, may be developing long-range missiles and could possess chemical and biological R400 aerial bombs and Scud missiles, and even smallpox.

Jack Straw, the Foreign Secretary, told his fellow Security Council Foreign Ministers that the document was a"chilling read".

General Powell resorted to reading passages from the paper out loud in the Council chamber. He pointed out that it chronicled nearly 30 times when Iraq had failed to provide credible evidence to substantiate its claims, and 17 instances when inspectors uncovered evidence that contradicted those claims. But his draft copy, dating from a meeting of the inspectors' advisory board last week, did not contain the crucial passage about the new drone.

The decision by Dr. Blix to declassify the internal report marks the first time the U.N. has made public its suspicions about Iraq's banned weapons programs, rather than what it has been able to actually confirm. "UNMOVIC has credible information that the total quantity of biological warfare agent in bombs, warheads and in bulk at the time of the Gulf War was 7,000 liters more than declared by Iraq. This additional agent was most likely all anthrax," it says.

The report says there is "credible information" indicating that 21,000 liters of biological warfare agent, including some 10,000 liters of anthrax, was stored in bulk at locations around the country during the war and was never destroyed.

The paper, a collection of 29 "clusters" of questions for Iraq, offers some reassurance about Iraq's missing botulinum toxin, which UNMOVIC believed is "unlikely to retain much, if any, of its potency" if it has been stockpiled since 1991.